The present invention relates to a room temperature-curable organopolysiloxane composition or, more particularly, to a room temperature-curable organopolysiloxane composition capable of giving a cured silicone rubber useful as a material of so-called FIPG sealing in automobiles under contacting with lubricating oils, e.g., engine oil and gear oil, under vigorous agitation by virtue of the absence of any adverse influences on the foaming behavior of the oil due to the contamination of the oil with certain constituents dissolved out of the silicone rubber contacting with the oil. The invention also relates to a method for the preparation of such a room temperature-curable organopolysiloxane composition.
Traditional oil-resistant sealing materials used in and around automobile engines include cork, organic rubbers, asbestos and the like and these materials are used in the form of gaskets and packings. A problem in these materials in the automobile industry is the troublesomeness in the control of stockpile inventory and process control even by setting aside the disadvantage that the oil-sealability performance of these materials is not always quite reliable. Accordingly, these traditional oil-sealing materials have been mostly replaced with the so-called FIPG (formed-in-place gasket) sealing by utilizing a room temperature-curable organopolysiloxane composition or room temperature-curable silicone rubber which is a pasty or putty-like composition capable of being cured at room temperature into a cured silicone rubber. By virtue of the excellent properties of the room temperature-curable organopolysiloxane compositions, the FIPG sealing is highly evaluated, though not free from problems, in respect of the workability, sealability and heat resistance as compared with the traditional oil-sealing materials.
The most serious problem encountered in the use of a room temperature-curable silicone rubber for the FIPG sealing in automobiles is that, when the FIPG silicone rubber is in contact with the lubricating oil in an automatic transmission, in particular, in the front engine-front drive type cars which is integral with the differential gear, the oil contaminated with certain constituents of the silicone rubber sometimes foams seriously due to the vigorous agitation with the gears to be eventually prohibitive of the use of the FIPG sealing due to oil leakage. Although various attempts and proposals have been made to solve the above described problems, none is known as a room temperature-curable silicone rubber composition for the FIPG oil-sealing exhibiting high oil-resistant adhesive bonding.